About 20% of Marks & Spencer shareholders are expected to vote against the promotion of CEO Sir Stuart Rose to chairman at the company's upcoming AGM.

According to reports, shareholders are also preparing to vote against proposals to change M&S's boardroom incentive scheme. The new proposals would make it easier for directors to get big payouts, the Guardian reported.

Corporate governance watchdog PIRC told just-food that Sir Stuart's promotion to chairman goes against corporate governance best practice guidelines, which favour independent external candidates to fill the role.

"A number of institutional investors wish to send a strong message to M&S about the importance of best practice," a spokesperson for PIRC told just-food.

PIRC is advising shareholders on the resolution and told just-food that its pre-AGM report will be completed within one week.

M&S declined to comment on the shareholder unrest.